This invention relates to stratified materials (articles) and the process for manufacturing them in which felts or layers of fibers impregnated with resin powders are caused to polymerize and/or otherwise harden and thereby to bond the fibers and form a coherent article.
It is known that according to a process developed by the inventor of the present invention, it is possible to impregnate a loose felt or other layer of fibers uniformly with synthetic resin powders. The synthetic resin powders are finely subdivided and coat the fibers and adhere thereto. The loose felt or layer can be compressed by rolling to form a sheet. The sheet formed as a consequence of the rolling operation can be obtained in different thicknesses and with different weights per square meter. This sheet may then be heated by passage on a pair of foraminous conveyor belts through a tunnel wherein polymerization occurs as a consequence of the heating. The conveyor belts maintain the sheet under a slight pressure at the desired uniform thickness. Hot air is passed through the sheet, heating the sheet and causing polymerization of the resin and thereby bonding the fibers to one another. The sheet is thus transformed into a firm felt, the flexibility and elasticity of which can be regulated at will as a function of the quantity of the resins charged to the fibers. This process is disclosed in Pat. No. 3,200,181 issued Aug. 10, 1965.
It is also known that several types of resins having different melting points can be incorporated in the same manner in the sheets of fibers, and in general it is possible to incorporate any product or desired substance in very finely ground powder form, such for example as fire-proofing substances or materials, mineral ores, or asbestos or stone dusts.